It was quite ___accident that I met him; he was homeless and ___rags at that time.
| A．by; in | B．on; in | C．at; by | D．in; in |
On April 1, Jim tried to play a trick ______ his teacher but the teacher wasn’t taken _____.
| A．by; on | B．in; in | C．on; in | D．on; on |
Many children seldom communicate with adults, ________ it difficult for their parents to know what they are thinking about.
| A．making | B．makes | C．to make | D．made |
The headmaster demanded all the teachers ______ in the office.
| A．mustn’t smoke | B．did smoke |
| C．should smoke | D．not smoke |
—How was that?
—I was chatting on line ______ the power went out.
| A．because | B．while | C．as | D．when |
In order not to be disturbed, I spent three hours _______ in my study.
| A．locking | B．locked | C．to lock | D．to be locked |